Account for the following:
(A) Aniline cannot be prepared by the ammonolysis of chlorobenzene under normal conditions.
(B) N-ethylethanamine boils at 329.3K and butanamine boils at 350.8K, although both are isomeric in nature.
(C) Acylation of aniline is carried out in the presence of pyridine.
Answer
(A)
- In case of chlorobenzene, the C—Cl bond acquires a partial double bond character due to conjugation.
- This lends it stability and makes it quite difficult to break .
- So under the normal conditions , ammonolysis of chlorobenzene does not yield aniline .
- Therefore, we use indirect ways to obtain aniline through chlorobenzene.
(B)
- Primary and secondary amines are engaged in intermolecular association due to hydrogen bonding between nitrogen of one and hydrogen of another molecule.
- The intermolecular association is more in 1-1 primary amines due to the presence of three hydrogen atoms . Butanamine is a primary amine.
- In secondary amines there are two hydrogen atoms available for hydrogen bonding . So, the intermolecular association is less than that in primary amines .
- N-ethylethanamine is a secondary amine.
(C)
- Catalysts are added to reactions to speed up the process by making the reaction more likely to happen , that is, increasing its spontaneity .
- During the acylation HCl is formed during the reaction.
- A strong base, pyridine , is added in order to remove the Hydrogen from Aniline and form HCl .
This shifts the equilibrium to the right hand side, making the reaction more spontaneous.